Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1999-01-25
2004-05-18
Nguyen, Thong Q. (Department: 2872)
Optical: systems and elements
Lens
With variable magnification
C359S703000, C359S694000, C396S072000
Reexamination Certificate
active
06738198
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical-element holding mechanism and an image-shake correcting device adapted for use in an optical apparatus, such as an interchangeable lens for a single-lens reflex camera or the like.
2. Description of Related Art
To correct deterioration of lens performance resulting from manufacturing error, it has generally been practiced to arrange the lens-holding mechanisms of interchangeable lenses of single-lens reflex cameras to be suited for correcting optical axis deviations of lenses during a manufacturing process, i.e., for adjusting relative positions of a plurality of optical elements in a direction orthogonally intersecting an optical axis. The typical arrangement of the conventional lens-holding mechanism and a method generally employed for correction of the optical axis deviation are described below.
FIG. 1
shows the lens-holding mechanism which forms a part of a conventional interchangeable lens for a single-lens reflex camera. Referring to
FIG. 1
, a guide tube
1
is kept in a fixed position with respect to a film surface. A guide slot la is formed in the guide tube
1
to extend in the direction of an optical axis. A cam tube
2
is fitted on the outer side of the guide tube
1
in such a way as to be only rotatable around the optical axis. A cam slot
2
a
is formed in the cam tube
2
.
A first lens tube
3
holds a first lens
5
and has its outer side fitted in the inner side of the guide tube
1
. A roller
4
which engages the guide slot la and the cam slot
2
a
is attached to the first lens tube
3
with a screw. When the cam tube
2
is rotated around the optical axis, the roller
4
is moved accordingly at an intersection point of the guide slot la and the cam slot
2
a
to cause the first lens tube
3
to move in the direction of the optical axis.
A second lens tube
6
holds a second lens
7
. The second lens tube
6
abuts on the rear end face of an arm part of the first lens tube
3
extending rearward in the direction of the optical axis and is secured to the arm part by a screw
9
. The second lens tube
6
is thus arranged to move integrally with the first lens tube
3
when the first lens tube
3
moves in the direction of the optical axis.
In the lens-holding mechanism which is arranged in this manner, the relative positions of the first lens tube
3
and the second lens tube
6
are not exactly decided in the direction orthogonally intersecting the optical axis. In this direction, their positions are arranged to be roughly determined within a certain range. By virtue of this arrangement, optical axis deviations (eccentric deviations) of the first lens
5
and the second lens
7
, due to manufacturing errors of parts, can be corrected by adjusting the position of the second lens tube
6
relative to the first lens tube
3
in the direction orthogonally intersecting the optical axis in assembling them.
The method for adjusting and correcting the optical axis deviation of the lens-holding mechanism during a manufacturing process is next described. In making the adjustment, the guide tube
1
is secured to an adjustment tool body (not shown) before the second lens tube
6
and the first lens tube
3
are fixed in position with the screw
9
. Then, an adjustment tool
8
which is composed of an adjustment ring
8
a
, an urging ring
8
b
and an urging spring
8
c
is set. The adjustment ring
8
a
is fitted on the outer side of the lens holding part of the second lens tube
6
. Then, the adjustment ring
8
a
is movable with respect to the adjustment tool body in the direction orthogonally intersecting the optical axis. The urging ring
8
b
is fitted in the inner side of the adjustment ring
8
a
and is urged toward the second lens tube
6
by the urging spring
8
c
which is disposed between the adjustment ring
8
a
and the urging ring
8
b.
Therefore, the second lens tube
6
is held in a state of being pressed against the first lens tube
3
by the urging ring
8
b
. In other words, the first lens tube
3
and the second lens tube
6
are kept in a state of being spaced at a fixed distance in the direction of the optical axis.
The above-stated optical axis deviation can be corrected by moving the adjustment ring
8
a
in the direction orthogonally intersecting the optical axis to bring the second lens tube
6
to a desired position in this direction. After the second lens tube
6
is moved, by using the adjustment tool
8
, to the position where the optical axis deviations of the two lenses
5
and
7
are corrected, the screw
9
is tightened to couple the first lens tube
3
and the second lens tube
6
with each other in a state of having no optical axis deviation.
However, the conventional optical axis deviation correcting method has the following shortcomings.
Firstly, since the second lens tube
6
is arranged to be urged toward the first lens tube
3
by the urging ring
8
b
, the urging force is exerted on the first lens tube
3
or the abutting part of the cam slot
2
a
and the roller
4
. Then, the optical axis deviation is corrected in a state of having the first lens tube
3
and the roller
4
deformed by the urging force. Therefore, the instant the urging force by the urging ring
8
b
is removed, the deformed parts tend to resume their original shapes to bring back the optical axis deviation. In this state, the optical axis deviation can be hardly considered to have been accurately corrected in actuality.
Secondly, the accuracy of correction deteriorates due to deformation of parts taking place when the screw
9
is tightened. For example, at the first lens tube
3
, a part around the screw
9
is deformed by the tightening frictional force of the screw
9
, particularly in a case where a self-tapping screw is employed as the screw
9
. At the second lens tube
6
also, a part around the screw
9
is deformed by the frictional force of the head part of the screw
9
. If the adjustment tool
8
is removed in the state of having such deformation, the second lens tube
6
tends to move in the direction of moderating a stress generated by the deformation. The optical axis deviation thus hardly can be considered to have been accurately corrected also in this respect.
Thirdly, a frictional force generated at the abutting faces of the first lens tube
3
and the second lens tube
6
while the position of the second lens tube
6
is in process of correcting adjustment also causes deformation of the first lens tube
3
, which also deteriorates the accuracy of the correction.
Meanwhile, cameras are arranged nowadays to automatically perform all actions important for photo-taking, such as determining an exposure, focus adjustment, etc. Even a person who is unaccustomed to operating cameras, therefore, can take photographs with little possibility of failure.
Besides, factors of photographing failures have been almost completely eliminated by recent advancement of efforts to develop a system for correcting image shakes that often result from vibrations imparted to cameras.
Here, the system for correcting image shakes resulting from vibrations is briefly described. In taking photographs, the hands holding the camera generally vibrate within a frequency range from 1 Hz to 12 Hz. In order to take a photograph without any image shake despite such vibrations at the time of a shutter release, it is a basic concept to detect the vibration of the camera and then to vary the position of a correction lens according to the value of the vibration detected.
Therefore, in order to make it possible to take a photograph without image shakes under such condition, it is necessary to accurately detect the vibration of the camera and then to correct a change of the optical axis caused by the vibration of the camera by displacing a correction lens.
Theoretically, the vibration of the camera can be detected by means of a vibration detecting means for detecting acceleration, velocity, or the like and a displacement signal output means for outputting a displacement signal obta
Kashiwaba Seiichi
Sato Shigeki
Washisu Koichi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Thong Q.
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